1. Field of the Invention
The present invention relates to a device and method for anchoring surgical sutures and more specifically to a fixable suture anchor plate and a method for anchoring sutures in a tendon-to-bone repair.
2. Background
When soft tissue tears away from bone, for instance in a rotator cuff tear, reattachment becomes necessary. Various devices, including sutures alone, screws, staples, wedges, plugs and plates have been used to secure soft tissue to bone.
The “rotator cuff” is a group of four muscles, the teres minor, the infraspinatus, the supraspinatus and the subscapularis which work in conjunction to maintain the location of the humerus with respect to the scapula. The muscles of the rotator cuff attach to the scapula and their respective tendons attach to the tuberosities of the humerus forming a cuff. The attachment of these tendons around the humeral head permits the rotator cuff muscles to rotate the humerus. The rotator cuff muscles also oppose and balance against the forces of the deltoid and pectoralis muscles.
Studies indicate that the attachment site between tendon and bone is the weak link during the early healing period, and objective evaluation of rotator cuff repairs shows an approximate 30% rate of failure of secure healing between tendon and bone at 3 to 5 years postoperatively. Clinical studies establish the high rate of residual defects in surgically repaired rotator cuffs and therefore the need to improve devices and methods for these repairs.
When repairing a rotator cuff tendon to bone, one of two methods are most often used: 1) the bone-tunnel method, or 2) the suture-anchor method. Each of the two methods has its relative advantages and disadvantages, and neither can be considered ideal.
The bone-tunnel method involves using a sharp instrument, usually a drill, needle or awl, to create an entry hole near the site of tendon attachment, and an exit hole some distance from the tendon. Surgical sutures are sewn through the tendon, and the free ends of the sutures are then passed through the bone tunnels. Usually multiple bone tunnels are created, and multiple sutures are passed through these tunnels. The free ends of the sutures are then tied over the bone between the bone tunnel exit holes to secure the tendon to the bone. An advantage of the bone-tunnel method is that there is no foreign material left in the patient other than suture. One advantage of the bone-tunnel method as compared with suture anchor repair is that the method may result in superior tendon fixation.
A disadvantage of the bone-tunnel method in a rotator cuff repair is found in its adaptation and use in connection with the relative weak region of bone that is most convenient for tunneling, the lateral metaphyseal bone of the proximal humerus. The sutures used to repair the rotator cuff tendon may actually cut through the soft bone in this region, leading to failure of the tendon-to-bone repair. Devices that are designed to augment the lateral metaphyseal bone of the proximal humerus are held in position simply by the suture that is used for the tendon-to-bone repair. If the sutures were to break, or if the tendon repair were to fail, the hardware would be free to migrate, possibly leading to undesirable consequences.
The second method, the suture-anchor method, involves the use of a suture anchor, which is a screw-like device having an eyelet on one end through which surgical suture may be passed. The suture anchor is inserted through a small hole and screwed deep into the bone. The suture ends are used for securing the tendon to bone.
One advantage of the suture-anchor method is that the tendon-to-bone repair may be performed arthroscopically through a few small skin incisions. The bone-tunnel method requires a larger incision. While arthroscopic repair with suture anchors of smaller rotator tears has been shown to be successful, arthroscopic repairs of larger tears are more prone to failure.
While the use of suture anchors might provide more stable fixation than bone tunnels in some cases, the pull-out strength is still dependent upon the quality of the bone into which the suture anchor is inserted. One of the regions of bone that is most convenient for fixation, the lateral metaphyseal bone of the proximal humerus, is relatively weak. Suture anchors placed in this region are also more prone to pull out of the bone, leading to repair failure. Complications from suture anchor pull-outs range from discomfort to severe joint destruction. While the use of suture anchors has been touted as providing stronger fixation than that of the bone-tunnel method, this claim is debatable. Using suture anchors, the rate of rotator cuff repair failure is still substantial, especially for older patients whose quality of tendon and bone deteriorates with age.
Regardless of whether the bone-tunnel or the suture-anchor method is used, most surgeons feel that is important to optimize the blood supply of the tendon that is to be repaired. The blood supply to the rotator cuff is thought to come from two sources: 1) the bone to which it is attached, and 2) the bursa tissue that overlies the tendon. Due to the inflammatory state that is often associated with injury, the bursa tissue is often abnormal and therefore removed during shoulder surgery. This leaves the bone as the lone remaining blood supply. Though many of the details of the healing process are incompletely understood at this time, many surgeons feel that exposing the tendon to the blood and stem cells that are present in bone marrow likely contributes to successful tendon-to-bone healing. To stimulate such bleeding, the surgeon usually scrapes, drills, or otherwise removes part of the outer layer of bone in the region where the tendon will be reattached. This process is known as decorticating. The disadvantage of this process is that decorticating the bone also weakens it, making suture anchors more likely to come loose and bone tunnels more likely to fail.
Failure of tendon-to-bone repairs may also be attributable to tearing of the tendon by the sutures. Tearing may be reduced when the surgeon employs a suture method whereby a suture is passed through the tendon multiple times in opposing directions rather than with a single pass. When a suture is placed through a tendon with a single pass the suture tends to tear through the tendon much more easily than if the load is distributed by passing the suture through the tendon multiple times in opposing directions. This suture method is much more difficult to achieve when attempted arthroscopically than it is through an open incision, which is why some surgeons prefer to repair the rotator cuff through an open incision rather than arthroscopically.
There is a growing consensus that the ideal method of fixation of the soft tissue to bone would restore the surface area of the pre-injury interface between the soft tissue repair and the bone, recreating what is known as the tendon “footprint.” The footprint is defined as the surface area of bone onto which the tendon connects in a nonpathological state (e.g. before an injury). After surgical repair tendon fibers grow into the bone during the healing period. Having this ingrowth occur over the large surface area that makes up the footprint will lead to a stronger repair as healing occurs.
Suture anchors have been used by some surgeons to achieve a repair that is meant to aid in the restoration of the tendon footprint. According to this method, one or more suture anchors are fixed at the most medial aspect of the greater tuberosity next to the articular surface, and a second anchor or row of anchors is fixed lateral to the greater tuberosity. Sutures are tied across the row of suture anchors fixed at the most medial aspect of the greater tuberosity, and are then “bridged” over the tendon to the second row of anchors. This arrangement holds the tendon against the bone at a medial aspect of the footprint and at a lateral aspect of the footprint. In addition to restoration of tendon-to-bone contact across the footprint, another factor that may contribute to the higher success rates of this method compared to older methods is that the synovial joint fluid is prevented from entering the area of healing. Synovial joint fluid is felt by many to interfere with tendon-to-bone healing.
A need exists to provide a method and apparatus that optimizes tendon-to-bone interface while minimizing motion of the tendon relative to the bone at the interface of the tendon-to-bone repair. Similarly, a need exists to provide a method and apparatus that improves the restoration of the “footprint” of the pre-injury interface between the soft tissue and the bone in a tendon-to-bone repair. There is also a need to provide a method and apparatus that securely attaches the tendon to the bone so that flow of synovial fluid into the surface area of the footprint of the tendon-to-bone repair is minimized. A need also exists to provide a method and apparatus for tendon-to-bone repair that is specifically designed to account for the anatomy of the rotator cuff, proximal humeral bony anatomy and contour, and vascular supply of the humeral head. A need also exists for a method and apparatus for tendon-to-bone repair that allows for decortication of the bone in the area of tendon attachment in order to create an improved blood supply for the healing tendon. The apparatus should allow for strong fixation of the tendon to the bone despite the weakening of the bone that is associated with decortication.
A need also exists to provide a method and apparatus for tendon-to-bone repair that augments the proximal lateral humeral bone to prevent cutting through of the sutures that is secured to the bone with screws. Having the apparatus secured to the bone with screws minimizes the chances that the device would loosen, migrate, and cause injury to the patient. The apparatus should allow for improved fixation during tendon-to-bone repair, especially in soft bone. A need also exists for a method and apparatus that will prevent synovial joint fluid from entering the space between the tendon and bone at the repair site. In addition, a need exists for a device that minimizes the prominence of the knots that are created when surgical sutures are tied during tendon-to-bone repair. Finally, a need exists for a method and apparatus for tendon-to-bone repair that permits passage of a surgical suture and needle through the device after the device is secured to the bone.
Therefore an object of the present invention is to provide a method and apparatus for rotator cuff repair which will reduce or eliminate pull-out of sutures relative to the humerus. Another object of the present invention is to provide a method and apparatus for tendon-to-bone repair which will reduce or eliminate cutting of bone tissue by the sutures and distributes suture forces over a large area both at the bone surface and at the rotator cuff surface. Another object of the present invention is to provide a method and apparatus that increases contact forces at the tendon-to-bone interface while minimizing motion of the tendon relative to the bone at the interface of the tendon-to-bone repair. Similarly, another object of the present invention is to provide a “double-row repair” method and apparatus that improves the restoration of the “footprint” of the pre-injury interface between the soft tissue and the bone in a tendon-to-bone repair. It is a further object of the present invention to provide a method and apparatus for tendon-to-bone repair that is specifically designed to account for the anatomy of the rotator cuff, proximal humeral bony anatomy and contour, and vascular supply of the humeral head.
Additionally, an object of the invention is to provide a method and apparatus that minimizes the prominence of knots created when surgical sutures are tied during tendon-to-bone repair. Another object of the invention is to provide a method and apparatus that will provide strong tendon-to-bone fixation while still allowing the surgeon to decorticate the bone in the region that the tendon is to be attached in order to create a good blood supply for the healing tendon. Another object of the invention is to provide a method and apparatus that will prevent synovial joint fluid from entering the space between the tendon and bone at the repair site. Yet another object of the present invention is to provide a method and apparatus for tendon-to-bone repair that permits passage of a surgical suture and needle through the device after the device is secured to the bone.